Point-of-sale (POS) systems used by retailers to process transaction may be outdated and complex. The payment systems used by POS systems may be deeply integrated, and may not be easily upgradeable. This may make it difficult to integrate new ways of making payments, for example, payments using mobile computing devices such as smartphones, as the new payment types may need to be integrated with the POS system and the payment terminal, may require a change in cashier workflow, or may result in a compromised user experience. Some new payment system may require cashiers to bridge the gap between new payment systems and the retailer's POS systems. A cashier may need to type a transaction total into a new payment system after using the POS system to determine the total. The casher may then get a confirmation of payment from the new payment system, which the cashier must then input into the POS system, for example indicating a payment type of “cash” into the POS system.
Some retailers may use identity-based payment systems. These systems may allow a user, or customer, to make purchases with minimal interaction with a cashier. This may require communication between the user's smartphone and the store's POS system, and it may also require that the store change POS systems or integrate software onto their existing POS system, which may be cost prohibitive, time consuming, or both.